A phase II study to evaluated the efficacy and safety of repetitive daily intravenous doses of RSR13 administered to patients receiving cranial radiation therapy for glioblastoma multiforme" is a non-randomized, open-label, multi-center efficacy and safety study in patients receiving a conventional six-week course of cranial radiation therapy for glioblastoma multiforme. To be eligible for entry into the study, patients must have a histologically confirmed supratentorial grade IV astrocytoma (glioblastoma multiforme). The daily dose of RSR-13 will be 100 mg/kg at a concentration of 20 mg/mL administered over 30 minutes via a central venous access device. RSR-13 administration will begin on the first day of radiation therapy, occur every day of radiation therapy, and be timed so that the end of infusion occurs within 30 minutes of the start of radiation therapy. Patients will be assessed for safety, adverse events, and toxicities throughout dosing and radiation therapy and until progression of disease or death. The purpose of this study is to determine the efficacy, safety, pharmacokinetics and pharmacodynamics of multiple daily IV infusions of RSR13 at a therapeutically relevant daily dose (100 mg/dg) administered immediately prior to radiation therapy in patients with glioblastoma multiforme.